JPH01111896A - Surface treatment of stainless steel sheet - Google Patents

Abstract

PURPOSE:To pickle a stainless steel sheet with a pickling device for common steel and to carry out excellent surface treatment while keeping an active surface by passing the band stainless steel through a pickling tank and a water washing tank to surface-treat the steel without exposing the steel to the atmosphere. CONSTITUTION:The band stainless steel 1 is traveled, degreased, and washed with water. The steel 1 is then electrolytically pickled in the pickling tank 4 by applying a current through a conductive roll 7 to remove the scale and oxide film on the steel surface, and a cleaned and activated surface can be obtained. The pickled steel is pulled up from the pickling tank 4, and introduced into the water washing tank 5 through a seal box 9. The inside of the box 9 is filled with the inert gas or reducing gas from a gas nozzle 12, hence the pickled active steel surface is not oxidized, and the steel is introduced into the water washing tank 5. As a result, the conventional continuous pickling equipment for common band steel can be used as such as this strike-plating equipment.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for surface treatment of stainless steel plates.
More specifically, the present invention relates to a method of performing surface treatment on a stainless steel plate while the surface is activated, and can be used in all fields of surface treatment of stainless steel plates.

[Prior Art] It has been known for a long time to plate the surface of a stainless steel plate, and various strike plating methods have been proposed in which plating is performed while pickling after degreasing. However, since both methods use highly corrosive acids for plating, the plating equipment, electrodes, plating rolls, etc. are corroded by the acid, resulting in very high maintenance costs.

Furthermore, it has been known that a dense oxide film has been formed on the surface of stainless steel plates, and this enhances the rust prevention effect. However, the formation of such an oxide film becomes a very serious hindrance when performing surface treatments such as plating. Since it is quite difficult to remove the oxide film on the surface of a stainless steel plate during pickling, various pickling methods have been proposed. Method 1 of immersing the object to be plated in an acidic activation bath with a specific composition and then subjecting it to cathodic electrolytic treatment using a cathodic electrolytic bath to activate the surface.
110792' etc. However, even if such a special pickling pretreatment method is used and the pretreatment is carefully performed, it is very difficult to plate the surface with metal. The reason for this is that the surface activated by pickling or pretreatment is very easily oxidized by trace amounts of oxygen, and the oxide film is stable, making it difficult to plate and even if it can be plated again, the adhesion is not good. It's for a reason.

[Problems to be Solved by the Invention] The purpose of the present invention is to solve the above-mentioned conventional problems, and to provide a stainless steel plate with an active surface after pickling using a pickling device for ordinary steel. The object of the present invention is to provide a method for performing good surface treatment.

[Means and effects for solving the problems] In order to achieve the above-mentioned object, the present invention aims to solve the above-mentioned problems after pickling.

It is characterized by passing the stainless steel strip so that it does not come into contact with the atmosphere until it is washed with water and subjected to surface treatment, and in addition to this, oxidation is suppressed during washing.The main points are (1) In a method of continuously surface treating stainless steel strips, the space between the stainless steel strip being pulled up from the pickling tank and introduced into the washing tank, and the space between being pulled up from the washing tank and introduced into the surface treatment solution tank. This is a surface treatment method for stainless steel plates in which the stainless steel plate is passed through the plate while being maintained in an inert gas or reducing gas atmosphere, and then introduced into a surface treatment bath for treatment. (1) above, in which the surface is washed with water and then introduced into a surface treatment bath for treatment.
This is a surface treatment method for stainless steel sheets.

One aspect of the present invention will be explained below.

Stainless steel is very susceptible to forming an oxide film on its surface, and in particular on the active surface immediately after pickling, an oxide film will form immediately if oxygen is present, and this oxide film will inhibit plating and reduce plating adhesion. was revealed as a result of various research.

As a preventive measure, various methods of plating immediately after pickling have been proposed, but after pickling, washing with water is always necessary to avoid acid from entering the plating bath, and during this water washing, the surface of the stainless steel is oxidized. As described above, it is extremely difficult to apply plating immediately after pickling.

Therefore, various strike plating methods have been proposed6.However, as mentioned above, this strike plating method is highly corrosive and has the problem of corrosion of plating equipment, so it cannot be adopted immediately. With current continuous strip steel surface treatment equipment, surface treatment of stainless steel, especially plating, is extremely difficult.

FIG. 21 shows the relationship between plating properties, particularly plating adhesion, and the time the samples were left in the air in a wet state after pickling.

In this way, it can be seen that the plating adhesion deteriorates as the residence time in the air increases.

In particular, the time after rinsing before plating and the time before rinsing after pickling have a significant effect.

Based on this knowledge, the present inventors researched a method for achieving good plating on the surface of stainless steel sheets, and found that the stainless steel surface was placed in an inert atmosphere after pickling or pretreatment for plating. It was discovered that oxidation can be prevented by washing with water in the same state to strictly prevent oxidation before introducing it into the next plating process, and as a result, plating performance and plating adhesion can be greatly improved. . At the same time, the performance can be further improved by blowing an inert gas into the water tank during washing.

An example of an apparatus for carrying out the present invention is shown in FIG.

The entire plating equipment is the same as the plating equipment for ordinary steel strips, and the degreasing tank 2. Washing tank 3. Pickling tank4. Washing tank 52 Surface treatment liquid tank (plating bath)6. It consists of On the other hand, in order to carry out the method of the present invention, the pickling tank 4
Seal boxes 9 and 10 are disposed on the bath surface across the boundary between the washing tank 5 and the plating bath 5, and the boundary between the washing tank 5 and the plating bath 6, so that outside air can be shut off. A gas nozzle 12 is provided so that active gas or reducing gas can be introduced.

In addition, above the bath surface above the electrodes on the outlet side of the pickling tank 4 and the inlet side of the plating bath 6, oxygen intrusion from the electrodes is placed above the bath surface to prevent oxygen generated from the electrodes from entering the seal box during electrolytic treatment. A prevention cover 11 is provided. Furthermore, a gas nozzle 12 is provided in the washing tank 5 for blowing an inert gas (for example, N2 gas) into the washing tank.

When a stainless steel strip (hereinafter simply referred to as Steel 4; V) is passed through using such a plating equipment, it is degreased and washed with water.
The steel strip thus prepared is electrolytically pickled in the pickling tank 4 by passing electricity through the current-carrying roll 7, thereby removing scale and oxide film on the surface of the copper strip and cleaning it to obtain an active surface.

The steel strip after pickling is pulled up from the pickling tank 4 and guided to the next washing tank 5 via a seal box 9. At this time, an inert gas or a reducing gas is introduced into the seal box 9 from a gas nozzle 12 and filled. By this, the active steel 4;F surface after pickling is introduced into the washing tank 5 without being oxidized. The copper strip is washed with water in the washing tank 5, and by washing with water while blowing inert gas such as N2 from the inert gas blowing nozzle 12 into the water bath, oxidation of the surface of the steel strip during washing is further suppressed. The activity is fiber 1. The steel strip after washing is pulled out from the washing tank 5, passes through the seal box 10, and is sent to the next plating bath 6. In this case, too, a gas nozzle 12 is passed through the seal box 10 to inert the steel strip. By introducing gas or reducing gas and filling it, the surface of the active copper strip after washing with water is introduced into the plating bath 6 without being oxidized, and the surface of the steel sheet is plated in an active state.

In this way, the present invention can perform plating using the continuous plating equipment for ordinary steel strips, which is not equipped with strike plating equipment. This makes it possible to plate stainless steel sheets using a process called plating.

[Example] In order to improve the heat resistance of a stainless steel sheet, a stainless steel strip having 15% Cr-4, 5% AQ as steel components was electroplated with Ni. The following method was adopted as pretreatment. 2% NaOH using the plating equipment shown in Figure 1.
The steel surface of a 0.3 mm thick plate was degreased in an aqueous solution and washed with water, then cathodic electrolytic pickling was performed in a 10% 112SO4 aqueous solution, and the pickled copper strip was passed through a sealed box maintained in an N2 gas atmosphere. and introduce it into the washing tank without contacting the air.
The steel strip was washed in water saturated with nitrogen gas, and the washed steel strip was passed through a sealed box maintained in an N2 gas atmosphere to introduce the plating into the bath without being exposed to air.

Ni6 is then deposited by electroplating in a normal Watt bath.
μ plated. Table 1 shows the results.

Conventional method (the steel strip is passed through the atmosphere, then from the pickling tank to the water washing tank.

From the results shown in Table 1, the plated steel sheet produced by the method of the present invention has good plating adhesion.

The present invention has been described above with respect to the case of electroplating Ni on a stainless steel plate, but the present invention also applies to Cr, Cu,
It can be applied to general surface treatments such as metal plating, coloring treatment, coating, etc. of white metals, and similarly excellent treatment performance can be obtained. [Effects] Surface treatment of stainless steel sheets is used to improve corrosion resistance and heat resistance. , or to improve paintability or electrical properties. However, as mentioned above, since an oxide film tends to form on the surface, the adhesion of the surface-treated film is not good. Therefore, when the method of the present invention as described above is adopted, very good characteristics can be obtained.

Further, the present invention can be easily implemented by simply installing a seal box and a gas nozzle in a conventional plating apparatus for ordinary steel sheets.

[Brief explanation of the drawing]

Fig. 1 shows an example of the apparatus used to carry out the present invention, and Fig. 2 shows a stainless steel plate after pickling. It is a figure showing the relationship between the time (seconds) left in the air and the plating adhesion after metal plating. Patent applicant Nippon Steel Corporation

Claims (2)

[Claims] (1) In a method of continuously surface treating stainless steel strips, there is a space between the stainless steel strips being pulled up from the pickling tank and introduced into the washing tank, and a space between the stainless steel strips being pulled up from the washing tank and introduced into the surface treatment bath. A method for surface treatment of stainless steel sheet, characterized by passing the sheet through the space while maintaining an atmosphere of inert gas or reducing gas, and guiding it to a surface treatment liquid tank for treatment. (2) The method for surface treatment of a stainless steel sheet according to claim 1, wherein the washing tank is a washing tank in which washing is performed while blowing an inert gas.